Fuel tanks need to be externally vented for proper fuel flow during operation. This is most commonly done by venting them through tiny pores in the fuel caps or through tiny openings in the fuel cap threads. These vents are small enough to prevent fuel droplets that are splashing inside the fuel tank from escaping during normal use. Units that have liquid lying against the fuel cap for extended periods of time may experience small amounts of seepage in and around these vent areas.

It is NOT recommended that these products be stored or operated in such a fashion that any fuel in the tank is sitting against the fuel cap for longer than a few seconds or leakage through the vents in the cap may occur. Preferred storage positioning for these products is to position them laying flat with the cap pointing up. If the unit is to be stored vertically, it is recommended that the unit be drained of fuel before hanging vertically or is positioned in such a manner that any remaining fuel in the tank is below the fuel cap level.